Into the Water
by broken-hearts-always-lie
Summary: Cosima knew it was a ploy. She could only hope that her sisters stayed safe, wherever they were. She, on the other hand, was infatuated with the bait that was dangled in front of her to lure her into DYAD's grasp. After all, how bad could a scary corporation be if they had Delphine *freaking* Beraud on their team? ((Mermaid/Siren!AU))
1. Five Daughters

**AN: I've been playing with this idea in my head for a while now and I've finally decided to go ahead with it. Please let me know what you think! This is a short chapter just because I wanted to gauge the interest and test the waters (bad pun, sorry, not sorry).**

* * *

"These are the last of them?" Siobhan looks at the four strange eggs in the large incubator as Marion drops off another box of supplements for when they hatch.

"The last we could save, yes. One was unfortunately lost to the sea."

 _Oh, Jonathan..._

"Very well." Siobhan rakes a hand through her hair, glancing back at the small boat parked on the side of the island, "I'll take them."

* * *

They're hardly three weeks old when it happens. Exhausted beyond belief, Siobhan can no longer keep her eyes on the five babies and instead decides to take a (short) rest. Sarah, Helena, Alison, Cosima, and Elizabeth.

One egg led to a set of twins somehow... She couldn't explain it, yet, but she had every intention of finding out how it was even possible when Marion stops by again.

She'd stuck with three of the names her late husband had confessed to wanting if he ever had girls and named the other two Sarah and Alison simply because.. well, they were her children, too.

Even if her husband did give birth to them... which still something that confuses her to no end; but hey, equality means different things to different people, right? Either way, the lot of them had been running her ragged.

So when someone came into her house, Siobhan didn't wake up. Why would she? The only person that had ever known about their little island was Marion.

She does wake up, however, when all five begin wailing relentlessly.

The man she spots is standing over Sarah and Helena's joint-tank, holding one of them in his arms.

She wishes with every bone in her body that she had the energy to fight him and get her back into her tank where she'd be safe; but, she's unable to in her current condition.

She does, however, follow him out to the edge of the Island, fighting with every ounce of strength that she has until he smashes a rock over her head, leaving her unconscious for several hours on the beach.

The other four are safe and sound, hungry and disgruntled, but safe.

She calls Marion, desperately, and demands that the woman come out to check up on the four she has and help her find clues or any evidence she can find that might lead to who took Helena.

She won't stop searching; not until she finds her again.

* * *

 **Five Years Later - Toronto**

"Alright, bags, books... what are we missing?" Siobhan looks between Alison, Beth, and Sarah.

"Cosima's still asleep," Alison and Beth speak up at the same moment.

Siobhan curses under her breath, kissing each of the girls' foreheads quickly, "Go outside and wait in the car, chickens. I'll be out shortly."

 **...**

Siobhan flicks on the light to the girls' bedroom, spotting Cosima above Sarah's bunk, sitting up with her legs hanging over the railing, "Why aren't you ready, chicken?"

She already knows the answer.

"I can't get down," Cosima's all-but sniffling, attempting to press her weight against the small ladder once more only to fight a hiss at the pain that shoots through her leg.

"Alright... There's no need for tears." Siobhan soothes, helping her down once Cosima has her arms held out for her. Setting her down on Sarah's bed, she rubs her back patiently, "This is the third time this week. I think we should go ahead with Dr. Bowles' plan."

Cosima looks up at her with puppy-dog eyes, shaking her desperately, "N-no, please, I just need ta' get stronger."

"Which is exactly why you should go to California, chicken. You'll like it there," Siobhan watches as Cosima attempts to test her weight again on the floor, "They've got a great school by the hospital and we've already found a couple that can take you in during the school year."

"I don't wanna leave the others."

"You'll see them again soon, I promise." Ever since spraining her ankle, Cosima has been out for the count. It was bad enough it was painful for her daughters to walk; with the time Cosima had been bed-ridden by Marion's orders, Cosima's ability to endure the pain and walk steadily had already greatly decreased.

If they didn't intervene now, the outcome would definitely not be an easy go around for a siren who's spent almost the entirety of her life on land.

* * *

 **Twenty Years Later - California**

Cosima winces, reaching forward to take another step in order to fight off the almost unbearable pains in her feet. At least when they were in the air, they didn't hurt at all.

This should be easier by now, but every step and attempt to put most of her weight on her feet still felt like the bottoms of her feet were being stabbed by red-hot pins and needles.

"You're improving."

Cosima stops, looking up at her 'doctor' with a breathless chuckle and a small smile, "I suck at this."

"Yes, but you're getting better," Marion smiles as she watches Cosima's arms shake from her grip on the forearm crutches, keeping a close eye on her balance, "Your mother will be proud to hear... perhaps you could call her?"

"Mom doesn't need to worry about me." Cosima grunts, cursing under her breath when her arms momentarily begin to threaten to give out.

"Easy for you to say." Marion swallows her amusement.

 _She's just like her mother._

"... All parents worry about their children, Cosima. It's a fact of life."

"All parents can shove-" Cosima curses when her arms buckle, fighting the urge to scream when the full weight of her body is on both of her feet.

Marion's quick to her side, taking a firm grip on her forearms, "Easy. Breathe through it," Listening for the inevitable shudder as Cosima violently bites down on her lip to keep herself from making a noise, she waits for the younger siren's eyes to be on her before continuing, "Do you want me to get you your chair?"

"... No." Cosima closes her eyes, doing her best to take in a full breath, "I want to walk over to it."

Marion smiles, relief settling in her shoulders as she eventually lets the younger siren go, "Very well. Try your best."

 _Just like her mother._

* * *

"Cosima, we're gonna be late!"

"Speaking of little brothers," Cosima groans, already backing the manual wheelchair up before turning around to the door, "I gotta' go, sis. I'll talk to you later."

" _Yeah. Just stay away from the shore, Cos_ _._ "

Cosima fights a small smile as she pulls her dreads into a makeshift bun, keeping the phone balanced between her shoulder and ear, "And when has a little water pollution ever stopped me?"

* * *

Delphine Cormier hates boats. No, scratch that, she detests boats with every cell in her body.

Of course, she knew the yacht was unavoidable since their... _avant garde_ coworker always adamantly refuses to meet up anywhere else... like in a coffee shop or, who knows, maybe even the DYAD laboratory where they're supposed to be working together?

If only Ethan Duncan could get with the times.

It was cute, at first, but the entire thing was becoming vastly out of hand.

Ever since the fire he experienced in the lab at DYAD years before she even joined their company, Ethan Duncan hasn't set foot on land. Anything he needs is sent out to the luxury yacht and DYAD pays for it without little more than a moment's hesitation. Doctors, food, repairs, clothing, tech... anything and everything he needed was always sent over. She supposes it beats a lawsuit, but something tells her if any lawsuit were ever brought up against DYAD, whoever was 'wrongly accusing' them would mysteriously disappear.

She can only hope that she'll be one of the lucky few that retire with a pulse and enough money to live comfortably.

If not for her repulsive boss, she'd likely be dead by now.

At least he's not entirely bad...

"Ah, Delphine!" Ethan approaches her, pulling her out of her musings as she looks over the water, arms relaxed and resting on a safety railing, "It's been so long since you've come to visit. Tell me, how are your brothers, Cedric and..?"

"Albert." Delphine offers, doing her best to force a smile, "He and his wife are very happy, and Cedric is almost finished with college."

She doesn't hate him, after all.

She just hates his boat.

 **...**

"You want to transfer to _Toronto_?" Marion's brows raise, "You do realize it will be significantly colder, right?"

 _And Lake Ontario may be polluted like San Francisco (or worse)-_

"Yeah, I've already bought new coats for the trip." Cosima offers almost weakly.

Marion wasn't buying the 'Dude, I just broke up with my girlfriend' game, either.

"What makes you think this is a good idea?"

"I need a change of scenery.. look, I just need you to clear me for travel."

Marion sighs, leaning back in her chair as she looks down at her niece. The poor girl can hardly walk... "Have you thought this through? It might not be as accessible as San Francisco has been."

"If it's not, then I'll deal with it and if it gets that bad... I'll transfer back." Cosima shifts in her chair, "I just need something different right now."

Fighting the urge to rub her eyes, Marion sighs again, "Fine, but you will check in with me twice a week," She fights back her own amusement at Cosima's visible excitement, " _-and_ you _must_ keep me up-to-date with your vitals. The bracelet is mandatory once you're out there."

* * *

"How'd it go?" Scott watches as Cosima catches up with him, hands gracefully gliding over the wheels of her chair.

"We're set." Cosima flashes a smile up at him, canines briefly exposed.

It makes him almost shiver, forcing a recall of the last (and only) time he saw the fangs right next to them.

"Hey, you okay?" Stopping in front of him, Cosima cocks her head to the side curiously, "Need a check-up? B'cause the doc's right over there."

Scott feels his gut relax the second Cosima nods back towards the door she just came out of.

This is still his adopted older sister.

Not whatever she was when she was in the water.

"Yeah, I'm good... Drinks?"

"That bar on the shoreline, maybe?"

"You're not gonna hunt tonight, are you?" Scott asks almost timidly, shouldering his bag as they exit the hospital.

"Nah'," Cosima stops for a moment out of slight surprise, pushing it off as casually asking before continuing down the ramp, "I haven't ever actually..." _Killed anyone_. Otherwise, she'd probably be walking on land without a problem.

She almost feels a little hurt that he'd ask-

"I know," Scott interjects quickly, not wanting to be mistaken, "I just.. I don't know, people change. You never know."

* * *

"Ugh, I miss red..." Cosima's fighting an almost giddy smile as Scott hands over her drink.

"You're a bit of a lush... aren't you?"

She almost wants to tease that it's genetic.

But he wouldn't understand, as she hasn't told him very much about her sisters (as adults).

"Hey, what do you think about going to Bobby's bar once we-" Cosima squints, stopping dead in her train of thought when she catches sight of a nearby yacht. She moves forward, almost tempted to stand when she's barely able to make out the sound of another siren before she hears the unmistakable sound that follows, "Holy shit!"

Someone's screaming as they fall into the water.

 _Her_ water.

Nobody hunts in San Francisco without her knowing about it.

 _Not good._

She doesn't want to end up in some fucking aquarium if some idiot makes the humans suspicious of them ( _again_ ).

"Cosima?" Scott watches in confusion as Cosima stands up, taking off the oversized, light cardigan that she's been wearing all day.

"Spidey sense is tingling! Gotta go... watch my shit!" Cosima barely has time to strip off her skirt and top before she's in the water and off of the pier. It might be risky, but it's worth avoiding a murder.

She'd gotten away with convincing Emi not to do anything reckless up until now. If it's her...

Shit could get ugly.

"Cosima! This isn't cool!" Scott's already looking down towards where he last saw herf by the time Cosima makes it down to the bottom of the water, away from prying eyes as she manages to strip out of her underwear, forcing the air out of her lungs with practiced ease as she adjusts to the inevitable pain that follows. The water is as salty and disgustingly polluted as she remembers. The humans might not be able to sense it as well as they do, but it still manages to leave her wanting to swim further away from California as she heads out towards the unfamiliar yacht at record speed.

As long as they don't murder anyone, Marion had assured her that the police would stay away from them and even have their backs if they get into any trouble. If this was Emi acting out after their break-up, then they'd be in serious trouble... She always had trouble controlling herself when she was upset.


	2. Sissster

Delphine hears the slow, lulling song before she can see her.

Her _voice_... soft and silken despite the slightly rocky cuts in it with every syllable. It was like nothing she's ever heard before. It wasn't any wonder that she couldn't help but peer over the edge to look down at the woman from below.

Her skin is almost the color of algae, strangely translucent as she floats easily near the boat, beckoning her closer and closer over the railing until the singing stops.

The next thing she knows, she's falling (and screaming) as she goes head first over the railing and into the water.

She hasn't been in the water in years and the tail that swiftly lashes over her head leaves her underwater, quickly losing air as she struggles to remain conscious and attempts to swim to the surface.

Her limbs feel like lead.

 **...**

Cosima swims forward at a near break-neck speed towards the yacht.

She almost stops when she feels Emi brushing against her, swimming behind her and towards the commotion.

 _At least it wasn't her._

She felt like a bitch for doubting her, though.

They continue forward, quickly in sync.

Emi manages to barely keep up with Cosima, something that only Beth could do (because of her lung capacity as a land runner).

When they're mere yards away from the chaos, Cosima changes direction, making quick gestures to Emi for her to deal with the attacker however she'd like before she's swimming off in her own direction, grabbing the body and pulling the woman against her back, never once minding the faint pain in the cartilage-like dorsal fins on her back.

She quickly swims out of sight for both privacy and safety, finding an area along the shoreline that's undisturbed by humans and lacking traffic. Hauling the woman to the shore, she quickly moves her onto her back, testing her breathing before feeling her gills relax.

The woman is breathing fine. No scary human CPR required (and thank god because getting Scott over here would take too long).

She _really_ needs to get certified, the amount of times this has happened in the past few years has become undeniably inconvenient.

Her head will definitely be bruised, but she doesn't look like she's in any dire danger.

So why is she finding herself staying?

It's the danger, she'll tell Emi and Scott later.

She doesn't want to risk the woman becoming unconscious or falling into a coma after all.

Totally not because she's drop-dead gorgeous even with the bags from a lack of sleep under her eyes.

Cosima rests back, groaning loudly before remembering to sink into the water until her torso is submerged.

It doesn't help, considering the change affects her entire body, but at least she won't have to explain the tail.

.. And she doesn't have to breathe out of her lungs like a human, which hurts during the change.

As if out of every cliche Cosima's ever seen on drowning victims, the woman in front of her sputters, coughing up a small amount of water as she comes to.

"Careful.."

She can't help but stay. Especially when warm eyes stare back at her.

Only, rather than a thank you, she's almost met with a rock to the face.

"Vous! Vous avez changé!" Delphine shouts, crawling back on the wet sand in an attempt to put distance in between her and the brunette.

Her hair was different.

She was blue, now.

Merde.

"Easy!" Cosima's hands are up in the air, sitting on her tail fin as she backs up slightly, "Dude, I have..."

Cosima shakes her head.

"I'm sorry. Can we just... do you speak any English?"

Delphine hesitates, brows furrowing as she lowers the rock halfway in the air.

Her voice is different, too.

"Oui," Delphine shakes her head momentarily, fighting a migraine, "Who... was that your sister?"

"What?" Cosima furrows her brows, "Did you see someone who looked like me?"

"Oui."

At least that narrows it down to a potential three.

Where's Emi? She should be back by now...

"I.. have a lot of sisters. It could have been one of them, but I doubt it."

"You.." Delphine drops the rock, panic subsiding as she looks the brunette over, "Êtes-vous une sirène? Ehm... _Mermaiden_?"

"I think you mean Mermaid," Cosima corrects almost shyly, offering her an apologetic smile as she visibly relaxes enough to return to her previous position, "And we prefer the term Siren."

"We? There are more of you?"

Cosima nods, "Yeah, look, can you just do me a favor and come up with a story to tell the others that doesn't involve me? We kinda like to stay out of the limelight."

Not her best moment.

"-Also, you're going to want to get that checked out by a doctor," Cosima gestures to her head, "Someone hit you pretty hard. Can you stand?"

"Ehm, oui, I think.." Delphine moves forward, getting up clumsily before swaying in her spot.

Cursing under her breath, Cosima shuts her eyes, "I don't s'pose you have a phone with a waterproof case on you, do you?"

Delphine shakes her head.

"Alright. Wait here. I have to check up on someone. Sit down and keep your knees up. I'll be back in a minute."

Delphine watches wide-eyed when the girl flips backward, almost disappearing in less than a second.

 _What just happened?_

 **...**

Emi watches as Cosima swims back to her quickly, remaining safely underwater, "What the hell, Cosima?"

"I have no idea, look, can you do me one last solid and go get Scott? The chick that was attacked has a concussion and she should go to the docs."

Emi blinks, eyebrows raising, "Wow, already moving on, Cosima?"

"Jesus, just- _Please_ , Emi? Whoever attacked her apparently looked like me. We can swap details later, but she's seen what I looked like and letting her see you could put us in more danger," Cosima swims towards her, staying under the cover of the trees around them.

 _Us_.

Emi hesitates, cursing under her breath as she looks around them, "Where is he at?"

"The peer by our favorite bar."

Emi sighs and rakes a hand through her cropped hair, "Fine. You owe me an explanation, though."

"Totally. Will do."

Emi doesn't look back.

She doesn't have to to know that Cosima is mostly speaking through gesticulations.

 **...**

Cosima swims back up to the woman, impeded by human legs, "You doin' okay?"

"Oui. It is easier to lay down." She raises her head to look her in the eyes, "You changed again..."

"Yeah. Happens when you don't want people to freak out." Cosima clambers up to her on her hands and knees, taking care not to fuck with her feet, "How's that head of yours?"

"Aching in waves," She watches as Cosima crawls next to her, head hovering above her as she examines the wound, "What's your name?"

"It's safer for you not to know," Cosima quips, cringing over her own words as she folds her legs, doing her best to cover herself modestly, "That's gonna leave one hell of a bruise, it's still surfacing. What's yours?"

"Delphine." She blurts without a moment's hesitation before blinking and blushing, "Ehm, Delphine. Delphine.. _Beraud_."

Her mother's maiden name. It's a little white lie but it will work in a pinch.

"You sure you're doin' okay, Delphine?" Cosima cocks her head to the side slightly, pulling the soaked black shirt Emi gave her closer around her.

"... ... Dizzy."

Cosima nods, "Just shut your eyes and keep talking to me. Where were you born? Do you have any family in town?"

"Ehmm... Lille. I don't have any family in town." Delphine does as she's told, rubbing the unbruised side of her forehead in an attempt to fight off the stress she feels growing in her muscles, "How... many are there of you?"

"There's just one of me." Cosima smiles, laying down on the sand before leaning back, "But there are... six that I've met so far."

"Just five?"

"What were you expecting, some crazy underwater civilization?" Cosima smiles, "Those of us living with humans tend to be pretty territorial, so we usually just keep to ourselves. Every once in a while we might meet someone, but it's pretty rare. We're usually only drawn to each other to mate."

"Oh," Delphine opens her eyes, looking up at Cosima curiously, "Does it hurt? Were you born this way?"

"Yes and yes." Cosima fights another tiny smile, "You're taking this surprisingly well."

"I've had enough existential crises in my life."

"Fair enough," Cosima shrugs before looking up, hearing the familiar brush of Scott pushing past plants in order to get to them, "Our help is here. Can you sit up?"

Delphine nods, breathing in shakily before doing so, putting no mind into the fact that her movements are clumsy.

She hopes she doesn't have anything serious-

" _Cosima?!_ " Scott comes brambling out of the tree line, racing up to her with her wheelchair folded under one arm and her pile of clothes in the other, "Are you okay? Did you-" Scott stops, catching sight of the blonde next to her, "Holy..."

"Yeah." Cosima grunts as she stands up, stumbling over to him before grabbing her clothes, eager to get changed and temporarily feeling less pain in her feet after the adrenaline rush that had ensued.

"Do you want me to get the chair..?" Scott watches, bug-eyed as Cosima pulls on her clothes.

"Can you help her stand, first? If she can't walk then we can just take an uber to Marion's." Her voice is at a whisper by the time she's putting her cardigan back on.

"Sure..."

...

"How is she?" Cosima looks up at Marion by the time she leaves the small room she brought Delphine into moments before, "Is she okay? How much did she remember?"

"One question at a time, Cosima. She should be fine, but we want to keep her under observation for a little longer. She didn't admit to much."

"Thank god.." Scott sighs, rubbing his forehead stressfully.

He loves his sister, but she has a knack for saving everything in sight that gets to him sometimes.

 _She could have been hurt, or worse..._

"Do you mind if I go in to speak with her?"

"Sure, just call if you need anything."

Cosima nods, pushing her chair towards the door only to stop when she hears Scott behind her, "You should stay back.. maybe go home early or go to the game tonight?"

Runewars with his buddies.

Shit. He almost forgot.

They'd been hounding him because he hadn't come in often enough recently...

"Sure."

 **...**

"Hey," Cosima offers Delphine a small smile when she enters her room.

"Allo..." Delphine croaks sleepily, settled into the hospital bed she'd been provided.

"Feeling any better?"

"Much, thank you." Delphine smiles back at her, "They will be keeping me here overnight."

Cosima nods, pushing her wheelchair over to Delphine's side of the bed, "Do you need to call anyone still?"

Delphine nods, thanking Cosima quietly when she's handed her phone before texting out a message to her boss, letting him know where she was.

"So, uhm," Cosima hesitates, watching as Delphine's fingers fly over the keyboard, "I feel pretty shitty about what happened... and was wondering if I could maybe make it up to you over brunch tomorrow?"

 _Wow. Smooth, Cos'._

Delphine stops mid-text, looking up at Cosima with a soft smile, "Sure. Let me just save my number in your phone once I'm finished."

...

Cosima rubs the back of her neck as she turns her chair so she can get into her bed easily, barely making it under the covers before she moans and shuts her eyes, relaxing almost immediately.

She hasn't felt this exhausted in... ages.

Who would hunt in her territory? They'd never had an issue with the others before...

Was it really one of her sisters? Or..?

God.

She needs to get baked and take a nice, long nap.

Cosima shifts in her spot, looking over towards the window.

 _Delphine_...

...

"Come again?" Sarah leans over the table slightly and into her mother's side in order to peer into the tiny camera on the laptop.

Marion fights the urge to bristle in annoyance at the sight of her as she nurses her drink, "A human girl."

Sarah snorts, arms folding as she shakes her head, current piece of laundry being abandoned on the table in favor of heading out the door as Sarah grumbles under her breath.

Both Marion and Siobhan only pick up the words 'high horse' and 'bloody well figures' before the door is slammed shut.

Marion and Siobhan meet each other's gaze for a moment, a small conversation being held in silence before Marion finally breaks it, intruding on the quiet, mostly-peaceful haven Siobhan's created for Sarah and Alison.

"He reached out to me a week ago. _They_ seem to intend on making a come-back. Should we tell them?"

"No. Don't do anything yet.." Siobhan's voice is patient when she finally musters together a coherent plan, "We need to see how this starts to play out..."

"But Cosima-your _daughter_ -"

"-Easy. She's had you as a teacher. She'll be fine, leech."

The nickname has become almost affectionate at this point.

Marion fights a nervous fidget, eyeing Siobhan quietly. She's older now, almost approaching her own body's age.

Yet she's all and more of the woman her brother had become so deeply enamored with.

 _"They're her **children** , Marion..."_

"I'll leave the decision to you, sissster."

Siobhan looks up when she hears the hiss at the end of Marion's words, unable to help the slight smirk before ending the call.


End file.
